How do you find all the zeros of f(x) = x^2 - 4x - 60f(x)=x24x60 with its multiplicities?

1 Answer
Apr 6, 2016

f(x)f(x) has zeros at x=6x=6 and x=-4x=4 (there are only 22 zeros including multiplicity)

Explanation:

Factoring
color(white)("XXX")f(x)=x^2-4x-60XXXf(x)=x24x60

color(white)("XXXXX")=(x+4)(x-6)XXXXX=(x+4)(x6)

When f(x)=0f(x)=0
either
color(white)("XXX")(x+4)=0 rarr x=-4XXX(x+4)=0x=4
or
color(white)("XXX")(x-6)=0 rarr x=+6XXX(x6)=0x=+6

Since f(x)f(x) is a quadratic (i.e. of degree 22)
it has (including multiplicity and possible complex values) exactly 22 zeroes.